If you built the Clipped wing version of the Lanier T-craft ( the 87 inch span ), then yes a YS 120 four stroke will fly it no prob. But the full 9ft span T-craft comes in at roughly 18 to 22 pounds with no motor unless you did some serious lightening of the air frame. Now it could be just me with my choice of covering { 21"s century fabric } so film covering probably shaved off a few pounds. But those 3 extra bays on each wing tip adds a lot of drag. As to the comment of " Some people are addicted to gasoline and oversized engines" they have OBVIUOSLY never heard the old saying, "there's NO such thing as too much power!" You can always throttle back if needed but you CAN'T add it if you don't have it and need it!